U.S. patent application number 16/633627 was filed with the patent office on 2020-07-02 for blow-formed container having inner surface provided with oil film for use.
This patent application is currently assigned to TOYO SEIKAN CO., LTD.. The applicant listed for this patent is TOYO SEIKAN CO., LTD.. Invention is credited to Yosuke AKUTSU, Ikuo KOMATSU, Keisuke NYUU.
Application Number | 20200207503 16/633627 |
Document ID | / |
Family ID | 65271993 |
Filed Date | 2020-07-02 |
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United States Patent
Application |
20200207503 |
Kind Code |
A1 |
AKUTSU; Yosuke ; et
al. |
July 2, 2020 |
BLOW-FORMED CONTAINER HAVING INNER SURFACE PROVIDED WITH OIL FILM
FOR USE
Abstract
The present invention aims to provide a blow-formed container
having an inner surface coated with an oil-based liquid so that an
oil film can be formed uniformly on the entire inner surface of the
container, thereby preventing or reducing effectively adhesion or
residue of a content onto the inside of the container. The
blow-formed container is formed of an olefin resin and has an inner
surface 1a having oil droplet dispersion of not less than 5.0 mm
when the oil droplet dispersion is defined as a length of an oil
droplet of medium-chain triglyceride used as a reference oil
retained at 23.degree. C. and dropped by 0.8 .mu.L onto the inner
surface.
Inventors: |
AKUTSU; Yosuke;
(Yokohama-shi, Kanagawa, JP) ; NYUU; Keisuke;
(Yokohama-shi, Kanagawa, JP) ; KOMATSU; Ikuo;
(Yokohama-shi, Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYO SEIKAN CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
TOYO SEIKAN CO., LTD.
Tokyo
JP
|
Family ID: |
65271993 |
Appl. No.: |
16/633627 |
Filed: |
July 18, 2018 |
PCT Filed: |
July 18, 2018 |
PCT NO: |
PCT/JP2018/026905 |
371 Date: |
January 24, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29B 2911/14093
20130101; B29B 2911/1408 20130101; B32B 27/08 20130101; B65D 1/0215
20130101; B29C 49/06 20130101; B65D 1/02 20130101; B32B 27/32
20130101; B65D 65/42 20130101; B29L 2031/7158 20130101 |
International
Class: |
B65D 1/02 20060101
B65D001/02; B29C 49/06 20060101 B29C049/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 2017 |
JP |
2017-154997 |
Claims
1. A blow-formed container having an inner surface formed of an
olefin resin, the inner surface has an oil droplet dispersion of
not less than 5.0 mm where the oil droplet dispersion is defined as
the length of an oil droplet of medium-chain triglyceride used as a
reference oil retained at 23.degree. C. and dropped by 0.8 .mu.L
onto the inner surface.
2. The blow-formed container according to claim 1, wherein the oil
droplet has a length/breadth ratio in a range of 1.000 to
1.010.
3. The blow-formed container according to claim 1, wherein the
inner surface formed of the olefin resin includes a smooth surface
having an arithmetic mean height Sa and a root mean square height
Sq both of which are not more than 1.5 .mu.m.
4. The blow-formed container according to claim 1, wherein an
oil-based liquid is coated on the inner surface of the container
prior to filling the container with a content.
5. The blow-formed container according to claim 4, wherein the oil
film of the oil-based liquid formed on the inner surface has a
thickness in a range of 0.5 to 30 g/m.sup.2.
6. The blow-formed container according to claim 4, wherein the
oil-based liquid is an edible oil.
Description
TECHNICAL FIELD
[0001] The present invention relates to a blow-formed container
provided with an oil film on its inner surface so as to be made
ready for use.
BACKGROUND ART
[0002] Since plastics can be shaped easily in a simple manner for
various embodiments, they are used widely in various fields. In
particular, olefin resins such as low-density polyethylene are used
to form an inner wall surface of a container like a directly
blow-formed bottle. Because of its squeezing property and
squeezing-out property, such a directly-blow shaped bottle is used
widely for containers to contain particularly viscous fluid
substances like ketchup and mayonnaise.
[0003] Meanwhile, a container to contain a viscous fluid substance
is required to have an inner surface that exhibits a high lubricity
to contents, so that the contents can be rapidly discharged and
used up without residing within the container.
[0004] In a conventional technique, the lubricity is imparted by
blending an additive such as a lubricant in the resin used to form
the inner surface of the container. In various techniques proposed
recently, a liquid film is formed on the substrate surface of resin
so as to improve the surface properties such as lubricity to a
viscous substance (see Patent document 1 for instance).
[0005] The techniques are currently attracting attention since they
can improve remarkably the lubricity in comparison with a technique
of blending an additive like a lubricant in a resin to form the
substrate surface.
[0006] In this technique of improving the surface properties by
forming a liquid film on the surface, it is required to retain
stably the liquid film on the surface. For this purpose, in the
aforementioned Patent document 1, fine ruggedness is formed on the
surface.
[0007] The fine ruggedness can be formed usually by spraying,
before forming a liquid film, a substrate surface with a coating
liquid like an ethanol solution in which inorganic fine particles
are dispersed, and then, by drying the surface. Alternatively, a
resin composition blended with inorganic fine particles is used as
the resin for forming the substrate surface. The resin composition
is subjected to a shaping process like stretching, thereby
producing a substrate having a predetermined shape (e.g., a
container) (see Patent document 1 or Patent document 2, for
instance). According to the techniques, a predetermined ruggedness
may be formed on a substrate surface in accordance with the
particle size and blend amount of the inorganic fine particles
blended in the resin forming the substrate surface.
[0008] However, when the liquid film is formed to improve lubricity
to the viscous substance as mentioned above, the liquid film on the
surface may sometimes be formed unevenly to cause a failure that
the viscous substance may adhere to a part of the substrate
surface. In particular, in a case of forming a film of an oil-based
liquid (oil film) on the substrate surface to improve the lubricity
to the viscous hydrous substance, the problem is more likely to
occur.
PRIOR ART DOCUMENTS
Patent Documents
[0009] Patent Document 1: JP 5971337 [0010] Patent Document 2:
JP-A-2015-227012
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0011] Therefore, an object of the present invention is to provide
a blow-formed container that can exhibit stable lubricity to the
content and effectively prevent or reduce adhesion or residue of
the content onto the inner surface of the container. The container
can be produced by coating an oil-based liquid on the inner surface
so as to form uniformly an oil film on the entire inner surface of
the container before filling the container with the content.
Means for Solving the Problems
[0012] The present inventors repeated experiments and reviews on
the blow-formed container to be provided with an oil film on its
inner surface in use. A blow-formed container has an inner surface
of an olefin resin formed to have a certain level of smoothness,
without adding a lubricant to the olefin resin. The present
inventors found that an oil-based liquid in the container spreads
wet to form a uniform oil film on the entire inner surface, thereby
arriving at the present invention.
[0013] The present invention relates to a blow-formed container
having an inner surface of an olefin resin. The inner surface has
an oil droplet dispersion of not less than 5.0 mm where the oil
droplet dispersion is defined as the length of an oil droplet of
medium-chain triglyceride used as a reference oil retained at
23.degree. C. and dropped by 0.8 .mu.L onto the inner surface.
[0014] It is preferable in the blow-formed container of the present
invention that:
(1) the oil droplet has a length/breadth ratio in a range of 1.000
to 1.010; (2) the inner surface formed of the olefin resin includes
a smooth surface having an arithmetic mean height Sa and a root
mean square height Sq both of which are not more than 1.5 .mu.m;
(3) an oil-based liquid is coated on the inner surface of the
container prior to filling the container with a content; (4) the
oil film of the oil-based liquid formed on the inner surface has a
thickness in a range of 0.5 to 30 g/m.sup.2; and (5) the oil-based
liquid is an edible oil.
Effects of the Invention
[0015] At least the inner surface of the blow-formed container of
the present invention is formed of the olefin resin. The container
is characterized in that the oil droplet dispersion (length of oil
droplet) measured by using the aforementioned reference oil is not
less than 5.0 mm. Namely, when an oil-based liquid (e.g., edible
oil) is coated on the inner surface of the container exhibiting the
oil droplet dispersion, the oil-based liquid rapidly spreads wet,
thereby forming an oil film uniformly on the entire inner surface
of the container. In particular, a thin oil film can be formed
uniformly by coating a small amount of oil-based liquid, and this
can avoid effectively variations in thickness caused by the flow of
the oil-based liquid that forms the oil film. As a result, the
lubricity imparted by the oil film to the content in the container
can be improved stably.
[0016] Therefore, the blow-formed container of the present
invention can be applied preferably for containing viscous hydrous
substances such as ketchup, mayonnaise, and dressing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1: a schematic side cross-sectional view showing a
preferred layer structure of container wall of a blow-formed
container of the present invention, in a state where an oil film is
provided on its inner surface.
MODE FOR CARRYING OUT THE INVENTION
[0018] The blow-formed container of the present invention as shown
in FIG. 1 has an inner layer 1 that forms the inner surface and an
outer layer 3 that forms the outer surface, and an intermediate
layer 5 is provided between the inner layer 1 and the outer layer
3. The blow-formed container having this layer structure is
provided with an oil film 7 on its inner surface 1a to enhance
lubricity (dischargeability) to a hydrous substance, and the
container filled with the hydrous substance is ready for use.
<Inner Layer 1>
[0019] In the aforementioned layer structure, the inner layer 1 of
the present invention is formed of an olefin resin.
[0020] For this purpose, olefin resins that have been well known
can be used. The examples include olefin polymers such as
low-density polyethylene, linear chain low-density polyethylene,
medium- or high-density polyethylene, polypropylene, poly1-butene,
and poly4-methyl-1-pentene; and copolymer resins or blends of these
olefins. Among them, the polyethylene having a density of not more
than 0.930 g/cm.sup.3 is particularly preferred as it has excellent
retention of the oil film 7 and flexibility, and also squeezing
property to extrude the viscous content. Examples of the
polyethylene are low-density polyethylene and linear chain
low-density polyethylene.
[0021] In the present invention, the inner surface 1a of the
container, which is formed of the olefin resin, is prepared so that
the oil droplet dispersion will be 5.0 mm or more. Here, the oil
droplet dispersion is measured using medium-chain triglyceride as
the reference oil. The reference oil kept at 23.degree. C. is
dropped by 0.8 .mu.L onto the inner surface 1a. As illustrated in
the following Examples, this oil droplet dispersion can be
calculated by dropping an oil droplet of the reference oil (0.8
.mu.L) onto the container inner surface 1a, and by observing the
size (length) of the oil droplet by use of a digital microscope 60
seconds after the dropping. A greater value indicates a higher
wettability to the oil-based liquid.
[0022] In other words, the inner surface 1a of the blow-formed
container of the present invention exhibits excellent wettability
to the oil-based liquid. This makes it possible to form an
extremely thin oil film 7 on the entire inner surface 1a of the
container uniformly by spraying a small amount of the oil-based
liquid.
[0023] The fatty acid in the medium-chain triglyceride used as the
reference oil in the measurement has a carbon number of 8 to 10. In
particular, the ratio of a fatty acid having a carbon number of 8
to a fatty acid having a carbon number of 10 may be 60:40, 70:30,
75:25, 85:15 and 100:0. The medium-chain triglyceride selected
therefrom has a viscosity in a range of 20 to 40 mPas at 23.degree.
C. This range can be employed suitably for measurement of the
aforementioned oil droplet dispersion, namely, it enables
measurement without substantial variations. In Examples below,
measurement of oil droplet dispersion is conducted using
medium-chain triglyceride having a viscosity of 33.8 mPas at
23.degree. C.
[0024] In the present invention, the measurement in the oil droplet
dispersion test is conducted as follows. It is particularly
preferable in the test that the length/breadth ratio of the oil
droplet is within the range of 1.000 to 1.010. The length/breadth
ratio within this range indicates that the oil droplet spreads wet
in a shape of almost an exact circle. As a result, the best
wettability can be obtained when the oil droplet dispersion is
within the range and at the same time the length/breadth ratio is
within the range.
[0025] The lubricity may be affected even by an extremely small
defect (micro-level oil cissing/crawling). For improving the
lubricity to the content in the container by using the oil film, it
is extremely important from the technical viewpoint to prevent the
micro-level oil cissing/crawling. Since the micro-level defects in
wetting are prevented effectively in the present invention, the
length/breadth ratio of the oil droplet is controlled to be within
the range in the oil droplet dispersion test.
[0026] In the present invention, imparting the oil droplet
dispersion as mentioned above indicates that a bleeding type
additive like a lubricant is not blended in the olefin resin to
form the inner layer 1. Usually, thermoplastic resins represented
by olefin resins contain a lubricant blended to impart
demoldability. If the lubricant is bled on the inner surface 1a, it
may repel the oil-based liquid coated on the inner surface 1a. As a
result, the oil-based liquid cannot spread wet. The olefin resin
may further contain inorganic oxide particles like silica blended
for the purpose of increasing the amount, reinforcing, or making
the inner surface 1a rugged. However, since the inorganic oxide
particles tend to make the inner surface 1a rugged, it may cause
micro-level defects in wettability of the oil-based liquid. In
order to develop the oil droplet dispersion, the olefin resin is
used to form the inner layer 1 without blending the inorganic oxide
particles.
[0027] Alternatively, the oil-based liquid as mentioned below can
be blended in advance in the inner layer in order to improve the
oil droplet dispersion.
[0028] Furthermore, in order to impart the oil droplet dispersion,
the inner surface 1a is required to have extreme smoothness. For
instance, the inner surface 1a is required to have arithmetic mean
height Sa and root mean square height Sq both of which are not more
than 1.5 .mu.m in measurement according to ISO25178-2:2012, and
more preferably, the maximal surface roughness Rz is not more than
20 .mu.m. Since the inner surface 1a is such a smooth surface, a
small amount of oil-based liquid may spread wet widely to exhibit
excellent oil droplet dispersion. From the viewpoint of preventing
fall of the oil-based liquid, this inner surface 1a preferably
might be roughened to have a great ruggedness. However, the
oil-based liquid might be difficult to spread wet on the surface,
thereby often causing problems such as variations in thickness or
the like.
[0029] The procedures for forming the smooth surface will be
described below.
[0030] In the blow-formed container of the present invention having
the inner layer 1, the thickness of the inner layer 1 is preferably
set not to exceed the required thickness as long as the properties
such as flexibility and strength required for the container are
satisfactory. Preferably, the thickness is not more than 200 .mu.m,
and particularly preferably in a range of about 40 to about 150
.mu.m. A thickness of more than the range may cause problems. For
instance, when an oil-based liquid is coated on the inner surface
1a of this inner layer 1, the amount of the oil-based liquid
absorbed in the inner layer 1 (saturated absorption) is increased.
This will increase the amount of the oil-based liquid necessary for
forming the oil film 7 of a predetermined thickness, or increase
the amount of the oil-based liquid to be absorbed in the inner
layer 1, whereby the thickness of the oil film 7 will greatly vary
over time.
<Outer Layer 3>
[0031] In the present invention, various thermoplastic resins to be
used for formation of containers can be used as the resin to form
the outer layer 3. For instance, various olefin resins and
polyester resins represented by polyethylene terephthalate can be
used. Among them, olefin resins are preferred from the viewpoint of
imparting flexibility to the container body so as to be squeezed
for discharging the viscous hydrous content. Most preferably, the
outer layer 3 is formed of an ethylene resin similar to that of the
inner layer, and particularly, low-density polyethylene (LDPE)
having a density of not more than 0.930 g/cm.sup.3.
[0032] The outer layer 3 is not required to exhibit properties like
oil droplet dispersion since no oil film is formed on the surface.
Therefore, various bleeding additives can be blended in the outer
layer 3, and a lubricant may be blended particularly preferably.
Blending a lubricant will make it possible to effectively avoid
disadvantages such as sticking of a container to another container
or to the conveyance belt during transportation of formed
containers.
[0033] Examples of the lubricants are described below. These
lubricants may be blended in commercially available polyethylene or
the like: [0034] fatty acids such as stearic acid and lauric acid;
[0035] aliphatic amides such as stearamide, palmitamide, oleamide,
erucamide, methylenebistearamide, ethylenebistearamide,
ethylenebisdocosanamide, and ethylenebisoleamide; [0036] fatty acid
esters such as butyl stearate, hydrogenated castor oil, and
ethylene glycol monostearate; [0037] alcohols such as cetyl alcohol
and stearyl alcohol; and [0038] soap scums such as zinc stearate
and calcium stearate.
[0039] The lubricant may be blended in an amount of about 0.01 to
about 0.5 parts by mass per 100 parts by mass of resin to form the
outer layer 3, for instance.
[0040] The thickness of the outer layer 3 is not required to be set
strictly as long as the properties necessary for the container,
such as flexibility, squeezing property or strength, can be
imparted.
<Intermediate Layer 5>
[0041] The blow-formed container of the present invention
preferably has a constitution as shown in FIG. 1 where an
intermediate layer 5 is provided between the inner layer 1 and the
outer layer 3. From the viewpoint of imparting the lubricity with
respect to the content, the container may have a single layer
structure consisting of only the inner layer 1 having the
aforementioned inner surface 1a to exhibit the oil droplet
dispersion. However, the blow-formed container having the single
layer structure has a high oxygen permeability, and thus, it is
unsatisfactory from the viewpoint of preventing oxidation
degradation of the content. For this reason, it is preferable to
provide the intermediate layer 5 of a resin other than the olefin
resin, thereby preventing or reducing permeation of oxygen.
[0042] Representative examples of the intermediate layer 5 include
a gas barrier resin layer and an oxygen-absorbing layer. Further,
an adhesive layer for bonding these layers to the inner layer 1 and
the outer layer 3 may be provided also as an intermediate layer. In
addition, a regrind layer or the like that includes scraps like
burr generated in the formation process can be provided as an
intermediate layer. It is also possible to provide both the gas
barrier resin layer and the oxygen-absorbing layer.
[0043] Examples of gas barrier resin used for forming the gas
barrier resin layer include ethylene vinyl alcohol copolymer
(saponified ethylene vinyl acetate copolymer), aromatic polyamide,
and cyclic polyolefin. Among them, the ethylene-vinyl alcohol
copolymer is most preferred since it is excellent in gas barrier
property.
[0044] An example of usually preferred ethylene vinyl alcohol
copolymer is a saponified copolymer obtained by saponifying an
ethylene vinyl acetate copolymer containing 20 to 60 mol % and
particularly in a range of 25 to 50 mol % of ethylene so that the
saponification degree will be not lower than 96 mol %, and
particularly not lower than 99 mol %.
[0045] It is also possible to use a blend of these gas barrier
resins.
[0046] The aforementioned gas barrier resin layer is capable of
preventing or reducing dispersion of the oil-based liquid that
forms the oil film 7 on the inner surface 1a. The gas barrier resin
layer is preferably used to effectively prevent transition of the
oil-based liquid from the inner layer 1 to the outer layer 3 side,
thereby stabilizing the oily film 7. The gas barrier resin layer
has another advantage, namely, it can prevent or reduce transition
of the lubricant blended in the outer layer 3 to the inner layer 1
side so as to keep the oil wettability of the inner surface 1a.
[0047] The oxygen-absorbing layer contains an oxidizable polymer to
be oxidized as a result of reaction with oxygen.
[0048] A detailed description of the oxidizable polymer is omitted
here because the polymer is well known and described in detail in
JP 2002-240813A and the like. Representative examples thereof
include: olefin resin having tertiary carbon atom (for instance,
polypropylene, polybutene-1 or their copolymers), thermoplastic
polyester or aliphatic polyamide; xylylene group-containing
polyamide resin; and polymer containing ethylenically unsaturated
group (for instance, polymers derived from polyenes such as
butadiene).
[0049] In this oxygen-absorbing layer, usually a small amount of
transition metal catalyst is blended to accelerate oxidation of the
oxidizable polymer. Representative examples of the transition metal
catalyst include inorganic, organic or complex salts of transition
metals such as iron, cobalt and nickel.
[0050] An adhesive resin layer is used to improve the adhesion of
the inner and outer layers 1, 3 to the gas barrier resin layer and
the oxygen-absorbing layer. The adhesive resin layer is formed of a
resin containing carbonyl group (>C.dbd.O) in the main chain or
the side chain for instance, and the carbonyl group is contained in
an amount of 1 to 100 meq, or in particular, 10 to 100 meq per 100
g of the resin. Specific examples of the resin include: olefin
resins graft-modified with carboxylic acids such as maleic acid,
itaconic acid, fumaric acid or their anhydrides, amides, esters, or
the like; an ethylene-acrylic acid copolymer; an ion-crosslinked
olefin copolymer; and an ethylene-vinyl acetate copolymer.
[0051] In the present invention, an olefin resin, in particular
polyethylene to be used for forming the inner layer 1 or the outer
layer 3 can be blended in the aforementioned gas barrier resin
layer or the oxygen-absorbing layer, in particular, the gas barrier
resin layer, as long as the properties of these layers are not
impaired. By blending the olefin resin, it is possible to improve
the adhesion between these layers to the inner and outer layers 1
and 3 without interposing an adhesive resin layer. The constitution
including no adhesive can be provided at a low cost.
[0052] The respective layers that may form the aforementioned
intermediate layer 5 are determined to have a thickness to
sufficiently exhibit their own functions.
[0053] Examples of preferred layer constitution of the blow-formed
container of the present invention, in which the aforementioned
intermediate layer 5 is included, are indicated below.
[0054] In the following layer constitution, LDPE indicates
low-density polyethylene having a density of not more than 0.929
g/cm.sup.3, RG indicates a regrind layer prepared by blending
virgin LDPE in scrap of burr or the like generated in the formation
process, GS indicates a gas barrier resin layer, and O2AB indicates
an oxygen-absorbing layer.
(Outside) LDPE/GS/O2AB/GS/LDPE (Inside)
(Outside) LDPE/GS/O2AB/RG/GS/LDPE (Inside)
[0055] In the layer constitution described above, it is possible to
provide the aforementioned adhesive resin layer on the interface of
each layer, although the adhesive resin layers can be omitted as
mentioned above in a case where LDPE is blended in the GS layer or
the O2AB layer.
<Production of Blow-Formed Container>
[0056] The blow-formed container of the present invention, which
has the aforementioned layer constitution and comprises the inner
surface 1a having a predetermined oil droplet dispersion, can be
produced by a well-known blow-formation method. A process that can
be employed for producing the container includes: preparing a test
tube shape preform by injection of a resin or resin composition to
form each layer, and subjecting this preform to a secondary stretch
blow formation. An alternative method is direct blow formation,
where a tubular parison is formed from a predetermined resin or
resin composition by melt-extrusion, the parison is closed at one
end by pinch-off, and then, a fluid like air is blown into the
parison to shape a container (bottle).
[0057] These methods for producing a blow-formed container have
been well known. The direct blow formation is particularly
preferred in production of a container since the method can impart
the container with flexibility and squeezing property for
discharging viscous contents.
[0058] In a case of producing the blow-formed container by direct
blow formation, it is preferable that the surface of a core mold is
not subjected to a treatment for repelling the molted resin or a
treatment with a highly slidable resin, because the surface of the
core mold will be brought into contact with the part of the inner
layer 1 that makes the inner surface 1a during the melt extrusion
to form the tubular parison. The surface treatment is conducted
usually by coating a heat-resistant fluororesin on the mold
surface, though the present invention is not limited to the
example.
[0059] In a biaxial stretch blow formation or the like, the preform
to be blown is formed by injection. In this case, the inner surface
of the preform to make the inner surface 1a of the container is
stretch-blown and shaped at a temperature not lower than the glass
transition point and lower than the melting point, and thus, highly
smooth surface can be obtained. On the other hand, in direct blow
formation, the inner surface of the tubular parison to make the
container's inner surface 1a is blown in the molten state and
shaped. As a result, the inner surface is considerably affected by
the surface roughness of the molten parison, and thus, it is
difficult to make the inner surface 1a as a surface having
predetermined smoothness. However, the tubular parison is formed by
melt extruding while keeping in contact with the core mold that has
been surface-treated so that the part to make the inner surface 1a
will repel a resin. Therefore, it is possible to form the smooth
inner surface 1a and to set the target oil droplet dispersion and
the target length/breadth ratio of the oil droplets within the
predetermined ranges.
[0060] The thus blow-formed container is usually sold directly to a
content vendor. The content vendor sprays an oil-based liquid on
the inner surface 1a of the container so as to form an oil film 7
on the inner surface 1a. After that, the container is filled with a
content, a cap is attached thereto for making the container be
commercially available.
[0061] That is, in the blow-formed container of the present
invention, the inner surface 1a exhibits high oil droplet
dispersion, so that the sprayed oil droplets widely spreads wet.
Therefore, with a small amount of oil-based liquid, a uniform and
thin oil film 7 is formed on the entire inner surface 1a of the
container, and retained stably. For instance, the thickness of the
oil film 7 (the amount of the oil-based liquid) present on the
inner surface 1a is maintained in a range of 0.1 to 30 g/m.sup.2,
or even thinner in a range of 0.5 to 10 g/m.sup.2. Usually, when
the container is held upright for a long time, a disadvantage may
occur, namely, the oil-based liquid may fall down to the bottom and
the oil film 7 on the body may disappear. However, since the amount
of the oil-based liquid is extremely small in this case, the
disadvantage can be prevented effectively. Furthermore, even when
the container is inverted to discharge the content, the oil-based
liquid present on the bottom of the container may be effectively
prevented from dripping so that the oil film 7 can be retained.
This can serve to prevent or reduce effectively another
disadvantage that the content adheres and resides onto the bottom
of the container.
[0062] Needless to note, the oil-based liquid is required to be a
non-volatile liquid having a low vapor pressure under atmospheric
pressure, for instance, a high boiling point liquid having a
boiling point of not lower than 200.degree. C., since a volatile
liquid would easily evaporate and disappear over time, which would
make it difficult to maintain the oil film 7.
[0063] Various specific examples of the oil-based liquid can be
presented as long as the liquid has a high boiling point as
mentioned above. In particular, when the oil-based liquid has a
surface tension considerably different from that of a viscous
hydrous substance to which the oil-based liquid is to keep its
lubricity, the oil-based liquid has a high wettability and can be
used suitably in the present invention.
[0064] For instance, it is preferable to use an oil-based liquid
having a surface tension in a range of 10 to 40 mN/m, in particular
in a range of 16 to 35 mN/m. Representative examples of the
oil-based liquid include glycerin fatty acid ester, liquid
paraffin, and edible oil/fat (edible oil). An edible oil/fat is
particularly suitable when the viscous hydrous substance is
food.
[0065] Examples of the edible oil/fat that can be preferably used
include soybean oil, rapeseed oil, olive oil, rice oil, corn oil,
safflower oil, sesame oil, palm oil, castor oil, avocado oil,
coconut oil, almond oil, walnut oil, hazelnut oil, and salad
oil.
[0066] As mentioned above, the multilayer blow-formed empty
container of the present invention has an inner layer 1 of a
suitable density of polyethylene and having an inner surface 1a
having excellent oil wettability. As a result, a slight amount of
oil-based liquid is sufficient to form a uniform oil film 7 on the
entire inner surface 1a, thereby exhibiting excellent lubricity and
dischargeability to the viscous hydrous content.
[0067] There is no particular limitation on the hydrous contents to
be contained in the container. However, since the container
exhibits excellent lubricity and dischargeability imparted by
formation of the oil film 7, particularly viscous hydrous contents
can be contained. The examples include ketchup, aqueous glue,
honey, various sauces, mayonnaise, mustard, dressing, jam,
chocolate syrup, yogurt, and cosmetic liquids like milky
lotion.
EXAMPLES
[0068] The effects of the present invention will be described below
with reference to Experimental examples.
[0069] The methods for measuring characteristics, physical
properties and the like in the Experimental examples, and resins or
the like used for forming the blow-formed containers are described
below.
1. Measurement on Surface Roughness of Bottle Inner Surface
[0070] A test piece of 10 mm.times.10 mm was cut out from the body
of the bottle formed by the method mentioned below, so as to
conduct a 3D shape measurement on the inner surface of the bottle
body by using a microscope (VK-100 manufactured by KEYENCE
CORPORATION). From the thus obtained data, the surface roughness of
500 .mu.m.times.500 .mu.m area (IS025178-2:2012) was
calculated.
2. Measurement on 2D Line Roughness of Bottle Inner Surface
[0071] A test piece of 20 mm.times.20 mm was cut out from the body
of the bottle formed by the method mentioned below, so as to
measure the roughness by use of a surface roughness measuring
instrument (SURFCOM2000SD3 manufactured by TOKYO SEIMITSU CO.,
LTD.) under the conditions of JIS'01, i.e., the length was 4 mm,
the cutoff was 0.8 mm and the velocity was 0.3 mm/s.
3. Oil Wettability Measurement
[0072] A test piece of 20 mm.times.20 mm was cut out from the body
of the bottle formed by the method mentioned below. By using a
solid-liquid interface analytic system (Dropmaster500 manufactured
by Kyowa Interface Science Co., Ltd.), 0.8 .mu.L of medium-chain
triglyceride was dropped on the bottle inner surface side of the
test piece so as to calculate the contact angle after 3 seconds. A
smaller value indicates better wettability at the time of
coating.
4. Measurement of Oil Droplet Dispersion
[0073] A test piece of 30 mm.times.20 mm was cut out from the body
of the bottle formed by the method mentioned below. 0.8 .mu.L of
medium-chain triglyceride was dropped on the bottle inner surface
side of the test piece, and the shape of the liquid droplets after
60 seconds was photographed by using a digital microscope (DVM5000
HD manufactured by Leica Microsystems GmbH) so as to measure the
shape (length-breadth) of the droplet at three points. For the
length, the median of the three points are recorded. For the
length/breadth ratio, all of the three points are recorded.
<Reference Oil>
[0074] Medium-chain triglyceride (MCT) (surface tension is 28.8
mN/m, viscosity is 33.8 mPas, both of which are measured at
23.degree. C.; boiling point is 210.degree. C. or higher, and flash
point is 242.degree. C. (reference value))
[0075] The surface tension of the liquid was measured at 23.degree.
C. using a solid-liquid interface analysis system (DropMaster 700
manufactured by Kyowa Interface Science Co., Ltd.). The density of
the liquid required for the surface tension measurement was
measured at 23.degree. C. using a density/specific gravity meter
(DA-130 manufactured by Kyoto Electronics Manufacturing Co., Ltd.).
Further, the viscosity of the lubricating liquid was measured at
23.degree. C. using a tuning-fork vibration viscometer (SV-10
manufactured by A&D Company Limited).
<Resin for Outer Layer Formation)
[0076] Low-Density Polyethylene-A (LDPE-A) [0077] Density: 0.921
g/cm.sup.3 [0078] Lubricant: oleamide 300 ppm blended
<Resin for Intermediate Layer Formation>
[0079] Low-Density Polyethylene-A (LDPE-A) [0080] Density: 0.921
g/cm.sup.3 [0081] Lubricant: oleamide 300 ppm blended
<Resin for Barrier Layer Formation>
[0082] Blended material of ethylene vinyl alcohol copolymer (EVOH)
and polyolefin
<Resin for Inner Layer Formation>
1) Low-Density Polyethylene-A (LDPE-A)
[0083] Density: 0.921 g/cm.sup.3 [0084] Lubricant: oleamide 300 ppm
blended
2) Low-Density Polyethylene-B (LDPE-B)
[0084] [0085] Density: 0.922 g/cm.sup.3 [0086] Lubricant: not
blended
Experimental Example 1
[0087] A 40 mm extruder-A was fed with a low-density polyethylene
(LDPE-A) as a resin for outer layer formation. A 40 mm extruder-B
was fed with a blended material (resin for barrier layer formation)
of an ethylene-vinyl alcohol copolymer (EVOH) and polyolefin. A 50
mm extruder was fed with a low-density polyethylene (LDPE-A) as a
resin for intermediate layer formation, and a 40 mm extruder-C was
fed with a low-density polyethylene (LDPE-B) as a resin for inner
layer formation. A polymer-coated core was attached to the
discharging side of the extruders from which a molten parison is to
be discharged, thereby extruding the molten parison from the
multilayer die head at 210.degree. C. The parison was then
subjected to direct blow formation at a mold temperature of
24.degree. C. to produce a bottle of 20 g comprising five layers of
five kinds with a 400 g capacity. The layer structure of the bottle
is as follows. [0088] Outer layer/adhesive barrier
layer/intermediate layer/adhesive barrier layer/inner layer
[0089] The thus prepared bottle was used to conduct a measurement
on the surface roughness of the bottle inner surface, the 2D line
roughness measurement of the bottle inner surface, oil wettability
measurement and oil droplet dispersion measurement.
[0090] The results are indicated in Table 1.
Experimental Example 2
[0091] A bottle was prepared in the same manner as in Experimental
example 1 except that a core without surface treatment was attached
to the discharging side for discharging the molten parison, and the
bottle was subjected to the respective evaluations. The results are
indicated in Table 1.
Experimental Example 3
[0092] A bottle was prepared in the same manner as in Experimental
example 1 except that the resin to be fed to the 40 mm extruder-C
for forming the inner layer was replaced by low-density
polyethylene (LDPE-A), and the bottle was subjected to the
respective evaluations. The results are indicated in Table 1.
TABLE-US-00001 TABLE 1 Surface roughness 2D line Inner layer
Surface 500 .mu.m .times. 500 .mu.m roughness material treatment
Sz/.mu.m Sa/.mu.m Sq/.mu.m Ra/.mu.m Experimental LDPE Polymer coat
10.63 1.06 1.35 0.134 example 1 (no lubricant) Experimental LDPE No
treatment 26.81 1.49 1.92 0.231 example 2 (no lubricant)
Experimental LDPE Polymer coat 8.87 0.61 0.78 0.095 example 3 (with
lubricant) Oil Oil wettability coatability Contact angle after Oil
droplet dispersion Total 3 s/deg. Length/mm Length/breadth
evaluation Experimental <10 7.11 1.009 1.007 1.000
.circleincircle. example 1 Experimental <10 7.10 1.017 1.062
1.013 .largecircle. example 2 Experimental 49.9 3.00 1.031 1.027
1.007 X example 3
[0093] In Experimental examples 1 and 2, low-density polyethylene
(LDPE-B) blended with no lubricant was used as the resin for inner
layer formation (inner layer material). Table 1 shows that the oil
wettability is less than 10 degrees and the oil droplet length is 5
mm or more in both of these Experimental examples. This result
demonstrates that the oil wettability in these Experimental
examples is superior to that in Experimental example 3 where a
lubricant is blended.
[0094] In Experimental examples 1 and 3, a surface-treated core,
i.e., a core coated with a polymer was used. The measurement result
on surface roughness shows that in these examples, both Sa and Sq
are not more than 1.5 .mu.m. This result indicates that the bottle
inner surfaces were extremely smooth in comparison with that in
Experimental example 2 using a core without such a surface
treatment.
[0095] In Experimental example 1, low-density polyethylene blended
with no lubricant (LDPE-B) was used as the inner layer material,
and a polymer-coated core was used. In this example, the oil
droplet dispersion (length/breadth ratio) was in a range of 1.000
to 1.010. This value is close to that of a true circle, indicating
that the micro-level wettability is excellent and that the thus
prepared bottle has excellent oil coatability.
EXPLANATIONS OF LETTERS OR NUMERALS
[0096] 1: inner layer [0097] 1a: inner surface [0098] 3: outer
layer [0099] 5: intermediate layer [0100] 7: oil film
* * * * *